Phototube



April 28, 1935- E. wALDscHMlD-r 2,039,134

April 2s, 1936.

E. wALDscHMlDT FHOTOTUBE Filed DeC. 6, 1932 2 SheeiS-Sheet 2 Figi . Unvenac':

Patented Apr. 1936 UNITED STATES PATENT OFFICE Application December 8, 1932, Serial No. 645,941 In Germany December 7, 1931 Thephoto-current generated in the known man-l ner by the light radiation is employed in the first place for controlling, for instance, a threeelectrode system. The anode of this system is 20 coated with fiuorescent or phosphorescent substances, which are caused to light by the electrons transmitted, dependent on the Anumber thereof. In this connection the corresponding strength of light is directly proportional of the 26 number of electrons which are transmitted per unit of time. The luminous rays thus created re-act on the photo-electric coating, and produce a correspondingly amplified photo-current, which in turn results in an increased passage of cur- 30 rent in the three-electrode system (amplifier system). The operation of the photo-tube according to my invention accordingly might be referred to as a photo-electric back-coupling. In the anode circuit of the amplifier valve there is 35 connected in the manner known any desired consuming apparatus or an additional amplifying arrangement. Naturally, if desired, there may also be connected between the photo-tube and the tube containing thev luminous coating causing 40 the back-coupling an .additional correspondingly equipped and dimensioned amplifying arrangement. In this case there is obtained by the amplied photo-current av considerably increased luminous radiation, and accordingly a more pow- 45 erful back-coupling. The arrangement last referred to may be employed with particular advantage in the case of systems operating with low frequency.

The invention is illustrated in the accompany- 50 ing drawings, in which Fig. 1 shows an embodiment of the photo-tube according to the invention, whereat the exciting light strikes against the photo-cathode I without touching the anode 4 of the amplifying system.

55 Fig. 2 shows a further embodiment of the pho- (Cl. 25o-27.5)

to-tube wherein the exciting light passes through the perforated anode of the amplifying system.

In Fig. 3 an arrangement is shown, wherein the photo-anode and the anode of the amplifying system are combined and form one common a'node 5 through which the exciting light is passing.

,. Fig. 4 shows an arrangement wherein. the

photo-system and the amplier system are arranged in two separate and spatially suitably coordinated valves.' l0

Fig. 1 shows particularly an electrode arrangement mounted in a glass vessel I on a press II, in which the exciting light strikes against the photo-cathode I. 'Ihe photo-current thus produced acts on the grid 5, which is directly conl5 nected to the photo-cathode I, and accordingly controls the amplifying system 3 and 5, 4. By reason of the electron current passing between 3 and 4 there is produced at the anode 4 which is coated with a luminous material a luminous radiation, which corresponds with the particular strength of current and acts on the photo-cathode I, and accordingly creates a photo-electric backcoupling. 2 is the photo-anode, which is directly connected with the anode 4. In the outer circuit the anode battery 6 and the heating battery 1 are provided. The grid 5 is connected to the cathode 3 across a leak resistance 8. 9 are the output terminals of the amplified photo-current.

In Fig. 2 the exciting light passes through'the 30 anode 4, which is perforated in screen-like fashion, on to the photo-cathode I. The anode 4 carries on its inner side the luminous coating, which is caused to light by the passage of the electrons and creates the back-coupling radiation, which strikes against the photo-cathode I. 2 is the photo-anode.

In the arrangement illustrated in Fig. 3 the photo-electric coating I is provided on the grid 5 itself. In this arrangement the light also 40 passes through the openings in the screen-like anode I2, which is coated with a luminous substance on the inner side. The photo-anode and the amplifying system anode are combined in this arrangement to form one anode.

Naturally, innumerable other possibilities of connection and forms of embodiment are conceivable. Thus, for example, it is possible to provide the photo-electric system and the amplifier system creating the luminous radiation in the same vacuum, or in two separate and spacially suitable co-ordinated valves.

An arrangement of this kind is shown in Fig. 4.

In this figure I3 is the container housing the photo-electric system and I4 the envelope con- 56 taining the amplifier system. The window is indicated by I2. The other parts are designed by the same numerals as the corresponding parts in thev foregoing figures.

In the first case it is desirable to employ high-vacuum photo-tubes. In the second case it is also possible to use photo-tubes filled with rare gas at the usual pressure. In arrangements such as described in conjunction with Figs. 2 and 3 it is desirable to employ perforated plates, the perforation area of which is equal to the surface coated with the luminous substance. prove to be desirable to increase the luminous area up to 8/10 or 9/10 of the complete area. At the same time it is also advisable to make the distance of the luminous anode from the photo-cathode as small as possible. 'I'he luminous substances employed, generally speaking, will be only those substances which possess the shortest possible after-lighting period. Accordingly, for the purpose of the invention, it is considered desirable to employ the chemically purest substances. The photo-cathode should be screened ofi against the light of the hot cathode. Failing this the photo-effect resulting from this luminosity requires to be compensated by a suitably selected grid bias.

I claim:

1. A photo-electric tube comprising an envelope including a window and housing a photoelectric cathode and an anode therefor, said cathode being mounted to receive light through said window, an amplifier comprising a thermionic cathode, a grid and an anode, said amplifier anode mounted parallel to and opposite said .photo- -electric cathode and having its surface facing said photo-electric cathode coated with a luminescent material, means connecting said grid with said photo-electric cathode, means connecting said anodes with each other and terminals to connect said electrodes with a suitable circuit.

2. A photo-electric tube comprising an envelope including a window and housing a photoelectric cathode and an anode therefor, said window mounted laterally with respect to said cathode, said cathode being mounted to receive light through said window, an amplifier comprising a thermionic cathode, a grid and an anode, said amplifier anode mounted parallel to and opposite said photo-electric cathode and having its surface facing said photo-electric cathode coated with a luminescent material, means connecting said grid with said photo-electric cathode, means connecting said anodes with each other and terminals to connect said electrodes with a suitable circuit.

3. A photo-electric tube comprising an envelope including a window and housing a photoelectric cathode and an anode therefor, said In certain cases, however, it may cathode being mounted to receive light through said window, an' amplifier comprising a thermionic cathode, a grid and a perforated anode, said amplifier anode mounted parallel to and opposite said photo-electric cathode between said cathode and said window and having its surface facing said photo-electric cathode coated with a luminescent material, means connecting said grid with said photo-electric cathode, means connecting said anodes with each other and terminals to connect said electrodes with a suitable circuit.

4. A photo-electric tube comprising an envelope including a window and housing a photoelectric cathode and an anode therefor, said cathode being mounted to receive light through said window, an amplier comprising a thermionic cathode, a grid and a perforated anode, said amplifier anode mounted parallel to and opposite said photo-electric cathode between said cathode and said window and having its surface facing said photo-electric cathode coated with a luminescent material, said photo anode and said anode of the amplifier being combined to form one structural unit, means connecting said grid with said photo-electric cathode, means connecting said anodes With each other and terminals to connect said electrodes with a suitable circuit. l

5. A photo-electric tube comprising an envelope including a window and housing a photoelectric cathode and an anode therefor, said cathode being mounted to receivelight through said window, an amplifier comprising a thermionic cathode, a grid and a perforated anode, said amplifier anode mounted parallel to and opposite said photo-electric cathode between said cathode and said window and having its surface facing said photo-electric cathode coated with a luminescent material, said photo cathode and said amplifier grid on the one hand and said photo anode and said amplifier anode on the other hand being combined to form structural units, means connecting said grid with said photo-electric cathode, means connecting said anodes with each other and terminals to connect said electrodes with a suitable circuit.

6. A photo-electric tube comprising an envelope including a Window and housing a photoelectric cathode and an anode therefor, said cathode being mounted to receive light through said window and an amplifier comprising a thermionic cathode, a grid and an anode having its surface coated with a luminescent material, said coated surface of said anode facing said photoelectric cathode, means connecting said grid with said photo-electric cathode, means connecting said anodes with each other, and terminals to connect said electrodes with a suitable circuit.

ERNST WALDSCHMIDT. 

